The present invention relates to a substrate treating system and a substrate treating method for selectively coating a substrate such as a semiconductor wafer or a substrate of a liquid crystal display (LCD) device with resist to form a resist pattern, followed by developing the pattern.
FIG. 1 shows a conventional resist coating/developing system used in the photolithography process in the manufacture of a semiconductor device. As shown in the drawing, the conventional system comprises a cassette station 210, a process station 220 and an interface section 230. Semiconductor wafers W are put in or taken out of a cassette CR by a wafer transfer device 211 mounted in the cassette station 210. A series of treatments with resist are applied to the wafers W in the process station 220. Further, wafers W can be transferred between the interface section 230 and a light-exposure device (not shown) arranged adjacent to the interface section 230.
The treating system of the construction described above is arranged within a clean room in which a clean air forms a down-stream. A down-stream of clean air is also formed within the treating system, as denoted by arrows in FIG. 1. Specifically, air intake chambers 210a, 220a, 230a are formed above the cassette station 210, process station 220 and interface section 230, respectively. Further, ULPA filters 210b, 220b, 230b are arranged below the air intake chambers 210a, 220a, 230a, respectively. Also, treating spaces are formed below these ULPA filters. As seen from the drawing, a clean air flows downward from the air intake chambers 210a, 220a, 230a into treating spaces through the ULPA filters 210b, 220b, 230b, respectively. Further, the clean air flowing downward through the treating spaces is discharged to the outside through a large number of air outlet ports 240 appropriately formed in a lower portion of the treating system. Incidentally, the air outlet port 240 formed in the cassette station 210 alone is shown in FIG. 1. However, air outlet ports are similarly formed in each of the process station 220 and the interface section 230, though these air outlet ports are not shown in FIG. 1.
In the conventional treating system shown in FIG. 1, it is impossible to form a uniform down-flow of the clean air through each of the cassette station 210, the process station 220 and the interface section 230. For example, an open portion 212 for the worker is formed on the left side in the drawing of the cassette station 210. Since the down-flow of the clean air within the treating system is weakened in the vicinity of the open portion 212, the particles generated from the worker, etc. enter the cassette station 210 through the open portion 212, with the results that these particles are likely to be attached to the wafer W. In this case, it is difficult to prevent sufficiently the particles from entering the system even if the clean air supply rate into each of the air intake chambers 210a, 220a, 230a is increased.
Also, in order to increase the cleanliness of each of the cassette station 210, the process station 220 and the interface section 230, it is necessary to control the inner pressure of each of these cassette station 210, process station 220 and interface section 230 so as to stop air flow among these members 210, 220, 230 and to allow the clean air to flow from these members to a clean room positioned outside these members.
In the conventional treating system, the inner pressure of each of the cassette station 210, the process station 220 and the interface section 230 is controlled by manually controlling the clean air supply rate into each of the air intake chambers 210a, 220a, 230a. However, the inner pressure of the treating system is changed by various factors including, for example, the door-opening during maintenance of the treating system, leading to a change in the differential pressure between the clean room and the treating system. It follows that the particles are likely to enter the treating system. A differential inner pressure also takes place among the cassette station 210, the process station 220 and the interface section 230, with the result that the particles are likely to enter the adjacent member among these members 210, 220 and 230.
FIG. 2 shows another conventional treating system 401. As seen from the drawing, treating units 407, 408 and a main arm (main transfer means) 406 are arranged within a single casing 410 in this treating system. An opening (inlet-outlet port) 403 for transferring a carrier (cassette) C into or out of the casing 410 is formed in the casing 410. The carrier C transferred into the casing 410 is disposed on a carrier station (table) 404. Then, the wafer W is taken out of the carrier C by a sub-arm (sub-transfer means) 405 and, then, transferred from the sub-arm 405 to the main arm 406. Further, the wafer W is transferred by the main arm 406 into the treating units 407, 408 successively in accordance with a predetermined recipe.
It should be noted that the conventional treating system 401 shown in FIG. 2 extends over two clean rooms CR1 and CR2, as apparent from the drawing. The particular treating system is generally called a through-the-wall type. To be more specific, the system 401 shown in FIG. 2 extends over first and second clean rooms CR1 and CR2 which are separated from each other by a partition wall 402. The first clean room CR1 is called a working zone the inner space of which is controlled at a high cleanliness. The carrier C is transferred into the system 401 and a controller is operated by a worker or a transfer robot within the working zone. On the other hand, the second clean room CR2 is called a utility zone. The cleanliness within the second clean room CR2 is set lower than that within the first clean room CR1 used as the working zone.
A wafer transfer port 403 of the system 401 faces the first clean room CR1. A carrier C introduced into the treating system 401 through the transfer port 403 is disposed on a table 404. Under this condition, the wafer W is taken out of the carrier C by a sub-arm 405 and, then, transferred from the sub-arm 405 onto a main arm 406 for further transference of the wafer W into the treating unit 407 for liquid treatment and the treating unit 408 for heat treatment, successively.
Fan-filter units (FFU) 409 each consisting of an integral structure including a fan and a filter are arranged in an upper portion of the treating system 401. The FFU 409 serves to cleanse the air within the first and second clean rooms CR1, CR2 so as to permit a clean air to be introduced into the casing 410 and to form a down-flow of the clean air within the system 401 such that the particles are substantially prevented from being attached to the wafer.
In the substrate treating system of the through-the-wall type, it is not absolutely necessary for the partition wall 402 to be positioned at the boundary between the carrier station 411 and the first process station 412. Specifically, a partition wall 402a may be used in place of the partition wall 402 such that the wall 402a forms a front wall of the system 410, as denoted by broken lines in FIG. 2. Alternatively, a partition wall 402b may be formed between the first process station 412 and the second process station 413, as denoted by broken lines.
When it comes to the substrate treating system of the through-the-wall type, the inner pressure of the first clean room CR1 used as a working zone is set higher by about 1.5 mm Aq (1.5 mm H.sub.2 O) than that of the second clean room CR2 used as a utility zone. As a result, formed is an air stream flowing from the wafer transfer port 403 toward the casing 410, even if a down-low of the clean air is formed by the FFU 409. It follows that the particles generated within the first clean room CR 1 are likely to flow into the treating units 407, 408 so as to be attached to the wafer W. Incidentally, these particles are likely to be generated when the carrier C is introduced into the system 410 and when the wafers W are taken out of the carrier C by the sub-arm 405.
In order to prevent the particle attachment problem, it is proposed to mount an openable door to close the transfer port 403 such that the transfer port 403 is kept closed except the time when the carrier C is transferred into or out of the treating system. Even in this case, however, the particles flow into the treating system through the transfer port 403 when the carrier C is transferred into or out of the treating system because the inner pressure of the first clean room CR1 is higher than that of the second clean room CR2.